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Core Grouting Services, an Acteon group company, has successfully completed a pipeline-free span rectification project in Trinidad and Tobago. Core installed grout bags at several subsea locations beneath a pipeline at water depths of 120-to-150 m.

Free spans on subsea pipelines are spans of the pipeline unsupported by the seabed and pipelines with long free spans are subject to increased fatigue loads and reduced pipeline integrity.

One method for correcting free spans is to install grout bags in the free span to support the pipeline. Grout bags are fabric formworks, which are positioned on the underside of the pipeline and then filled with a cement-based grout from a mixing and pumping unit situated on a support vessel. Once the bag is full, the flexible tether line is cut, activating the self-sealing valve on the grout bag inlet.

Ivan Harnett, managing director, Core, said, “Our client identified more than 50 locations on its subsea 24-in. pipeline where free spans required correcting with grout bags. We designed and manufactured customised grout bags to fit the free span locations. Because of the water depth and remote location, the grout bags were positioned by ROVs. We also supplied bag deployment frames, which enabled the bags to be lowered to the seabed and successfully positioned by the ROV. The installation of the grout bags at the identified locations brought known free spans under the allowable design limits.